In a known gas turbine engine, up to about 19% of air flow passing through a compressor apparatus of the gas turbine engine may be extracted. A piping system is provided for extracting the compressed air from the compressor apparatus. The piping system comprises a first set of four pipes circumferentially spaced apart about the compressor apparatus and axially located between sixth and seventh stages of the compressor apparatus and a second set of four pipes circumferentially spaced apart about the compressor apparatus and axially located between eleventh and twelfth stages of the compressor apparatus. The air may be extracted for any of several reasons, such as to remove a portion of the compressed air during startup to avoid compressor apparatus surge; provide cooling air for hotter sections of the gas turbine engine during normal operation; provide oxidizing air for an air-blown gasifier in an air-blown Integrated Gasification Combined Cycle (IGCC) plant; provide compressed air to a cryogenic air separation plant to produce oxygen for an oxygen-blown gasifier in an oxygen-blown IGCC plant.
U.S. Pat. No. 5,657,624, the entire disclosure of which is incorporated by reference herein, teaches using an ion transport membrane system in combination with a combustion turbine system so as to remove a portion of oxygen from compressed air supplied by a compressor apparatus forming part of the combustion turbine system.
A system is desired for extracting more than 20% of air flowing through a compressor apparatus or an intermediate section of a gas turbine engine without requiring lengthening of a rotor shaft extending between the compressor apparatus and a turbine apparatus of the gas turbine engine.